Police Minister Anne Tolley has asked officials to begin work on a sex offenders' register but concedes no system is immune to human error.

The Government's plans to launch a register were announced in April and Tolley has recently returned from Britain where she examined the way that country manages high-risk criminals.

The monitoring regime would be accessible to government agencies but not the public.

Police and Corrections were now developing a scoping report and timeline for the establishment of a register, she said today.

"It's quite a big piece of work. It's not just a list of offenders. It's actually a management system that manages offenders from the time they leave prison almost for the rest of their lives."

Tolley rejected criticism from Labour that the register would only contain information about sex offenders that was already available to the Ministry of Justice.

"It's about keeping track of where those people are, making sure they're supported long after their prison sentence or supervision order runs out because at the moment when that finishes, they disappear off into our communities and we literally wait for them to reoffend before we pick them up again."

The Government would have to ensure the system was secure, she said.

"It can be very detrimental to someone who is being well managed within the community, that suddenly a community finds out their history."

Ensuring secure access to the register had to be "separated out" from recent security and privacy breaches by ACC, Work and Income and Inland Revenue, Tolley said.

"There is always room for human error, you can't get away from that. You can design systems to be as secure as possible but if someone presses the wrong button with the internet today, you can send a message out very quickly.

"But it still behoves Government to make sure we have safe and secure systems and we have protection for individual privacy."

Tolley hopes to take a proposal to Cabinet by the middle of next year.